#include<cstdio>
using namespace std;
int mult5(int x)
{
    int nr=0;
    while(x%5==0)
    {
        nr++;
        x=x/5;
    }
    return nr;
}
int fact(int x)
{
    int s=0,p=5;
    if(x==0)
        return 1;
    while(x>mult5(p)+s)
    {
        s=s+mult5(p);
        p=p+5;
    }
    if(x==mult5(p)+s)
        return p;
    return -1;
}
int main()
{
    int n;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&n);
    printf("%d",fact(n));
    return 0;
}